The present invention relates to an aqueous flowable composition for fenazaquin. Fenazaquin is the generic name for 4-[2-[4-(t-butyl)-phenyl]ethoxy]-quinazoline. It is representative of a new and useful class of miticidal compounds disclosed in EPO Application 89300657.7, filed Jan. 25, 1989.
An aqueous flowable composition, or simply, an aqueous flowable, is one type of agricultural formulation. An aqueous flowable is a formulation typically comprising an active ingredient which is a finely ground water-insoluble solid displaying good storage stability and is stable in the dispersing medium. The formulation will also typically include some or all of the following: a surfactant, suspending agent, anticaking or flow aid, dispersant, defoamer, and freeze-point depressant, all of which are selected so that the formulation can be readily mixed in a liquid dispersing medium, such as water, or an anhydrous organic solvent such as mineral oil, fatty oils, or glycol ethers, to form a stable suspension suitable for spray application. These formulations are made by standard techniques, well known in the art.
The surfactant acts as a wetting agent to reduce the surface tension at the water-solid interface, and therefore increases the tendency of the water to contact the complete surface of the active ingredient particles. Both anionic and/or nonionic surfactants may play a role in the stabilization of a flowable formulation. For a water-based flowable, the surfactant must be water soluble, at least to the concentration limit desired for the lower temperature limit. Examples of surfactants include anionic surfactants such as alkyl polyether alcohol sulfates, arylalkyl polyether alcohol sulfates, arylalkyl sulfonates, alkylnapthalene sulfonates, and alkyl phenoxybenzene disulfonates, and nonionic surfactants, such as arylalkyl polyether alcohols, alkyl polyether alcohols, polyoxyethylene fatty acid esters, polyethylene sorbitan fatty acid esters, polyalkylene oxide block copolymers, polyalkylene oxide block copolymer monohydric alcohols, and polyalkylene oxide block copolymer alkyl phenols. Aqueous flowables typically contain 0.5-10% by weight of a surfactant.
The suspending agent acts as a thickening agent or thixotrope in maintaining the dispersed, micron sized particles of the formulation in suspension. The suspending agent is a water soluble or water dispersible anionic colloid possessing shear thinning properties, low sensitivity to temperature, good stability in both acidic and basic media, and is compatible with most inorganic materials. Examples of suspending agents include xanthan gums, organically modified montmorillonite clays, attapulgite clays, carboxy-vinyl copolymers, and cellulose ethers. Aqueous flowables typically contain 0.02-1% by weight of a suspending agent.
An anticaking agent or flow aid is a diluent which may be necessary to help improve the resuspensibility of the diluted spray, reduce the ultimate particle size of the active ingredient by acting as a grinding aid or lubricant in the milling process, modify the surface of the active ingredient thus inhibiting its crystal growth potential, and perform as a viscosity-modifying agent. Examples of anticaking agents or flow aids include kaolinite clays, diatomites, synthetic silicas, and attapulgites. Aqueous flowables typically contain 0-10% by weight of an anticaking agent or flow aid.
The dispersing agent is a polar organic material with surface active properties that orients itself between particles of active ingredient, and by virtue of size or charge, reduces the cohesiveness or attraction of the active ingredient particles for each other. In addition to imparting this physical stability to the aqueous mixture, dispersants may also aid in the redispersibility of the diluted spray mixture. The dispersing agent must be carefully selected and used to avoid problems such as foaming. Examples of dispersants include the salts of the lignosulfonic acids, the polymerized alkyl, arylalkyl or naphthalene sulfonic salts, and high molecular weight anionic surfactants. Aqueous flowables typically contain 0.1-2% by weight of a dispersing agent.
An antifoam agent, or defoamer, may be needed in the formulation if the surfactant or dispersant selected produces a stable foam when diluted with water. An antifoam agent may also be needed as a processing aid in milling to prevent aeration in the grinding stock dispersion because stable foamation during the milling process decreases the intimate contact between the grinding media and the active ingredient, thus decreasing grinding efficiency. Example of defoamers include the dimethylpolysiloxanes, ANTIFOAM A, ANTIFOAM C, ANTIFOAM FG-10, ANTIFOAM DB-100, AND ANTIFOAM AF-100 (Dow Corning). Aqueous flowables typically contain 0-1.0% by weight of a defoamer.
A freeze-point depressant may be necessary to ensure good low temperature stability. The more common examples of freeze-point depressants include ethylene and propylene glycol. However, sorbitol and glycerol may also be typically used. Functionally, in addition to lowering the freezing point of the water solvent, the freeze-point depressant may aid in preventing drying and skinning by acting as a humectant, controlling viscosity, removing hydrophobic impurities, and assisting the wetting process before and during milling. Aqueous flowables typically contain 2-10% by weight of a freeze-point depressant.
An antimicrobial agent may be necessary to prevent growth of bacteria, fungi, or other microbial organisms that can flourish in an aqueous environment. Also, the presence of xanthan gums, found in many aqueous flowable formulations, can accelerate the organism growth since the gums can act as a food source for the microbial organism. An example of an antimicrobial agent is PROXEL GXL (1,2-benzisothiazolin-3-one, ICI). Aqueous flowables typically contain 0-0.2% of an antimicrobial agent.
To facilitate handling and use, agrochemicals are not typically sold in the form of pure active ingredient or technical material, but instead, are typically sold as a formulated composition product. If the material is to be applied by spraying, it may typically be applied as an aqueous flowable. In such case, the product obtained by the applicator is a formulated product that can be readily mixed with water to form an aqueous flowable product. The product may then be applied from all types of presently used spray equipment.
Efforts to formulate fenazaquin as a conventional aqueous flowable formulation resulted in compositions of low miticidal activity. It was found that conventional aqueous flowable formulations resulted in a product that lost miticidal activity during storage. The low miticidal activity was found to be due to an unacceptable level of particle size growth during storage. Conventional aqueous flowable fenazaquin formulations were found to increase in particle size, apparently by crystal growth or Ostwald ripening, agglomeration, or by both. The size of the particles is important as the miticidal efficacy of an aqueous flowable fenazaquin product depends upon the average particle size remaining less than seven microns, or preferably, less than four microns.